FIELD OF THE INVENTION
The present invention relates to a liquid cooled cooling device which is attached to the heat generating section, for example, of a semiconductor device fabrication apparatus, and which is used for the cooling of the heat generating section using a cooling liquid such as cold water.
In, for example, a fabrication apparatus for semiconductor devices, countermeasures to the vibration and temperature accompanying an increase in the degree of integration of semiconductor integrated circuits, and furthermore, to the operating costs thereof, present difficult problems. For example, in processes for the formation of an integrated circuit with a superfine pattern on a wafer, even slight vibrations, which do not normally present a problem, can have a large adverse effect. In particular, superprecision apparatuses such as EB exposure apparatuses, which are necessary steps in the fabrication of superfine semiconductor devices, have an extremely large number of sources which generate vibration. There are various ways by which these vibrations may be propagated. In addition, the superprecision apparatus includes heat generating sections which generate a large amount of heat. A slight vibration caused by the sources that generate vibration and a change in temperature caused by the heat generating sections cause a slight variation, thermal expansion in an alignment stage, variation in the index of refraction of the optical path, etc. This can have extremely large effects on the accuracy of alignment. In addition, it is necessary to provide for heat dissipation with respect to heat generating sections, so that a cooling device is necessary.
Among such cooling devices, a device such as that shown in FIG. 7 is commonly known. In accordance with such a device, a cooling pipe RK comprising a thin metal tube which is in contact with the outer peripheral portion of the heat generating section HB, is wrapped therearound; cold water, which is used as a cooling liquid, flows into a flow-in portion LN at one end of this cooling pipe RK, and, after cooling, this cold water flows out from a flow-out portion LO at the other end of the cooling pipe RK. Here, the heat generating section HB exhibits a cylindrical form with a diameter of 300 mm and a length of 300 mm, and the cooling pipe RK is wound 15 times therearound. Accordingly, the water flow resistance of this cooling apparatus is 800 mmAq/m.times.14.1 m=11280 mmAq.congruent.1.1 kg/cm.sup.2.
In this case, if the temperature of the cooling liquid at the flow-in portion is represented by T.sub.1, and the temperature at the flow-out portion is represented by T.sub.2, it is common to set the temperatures T.sub.1 and T.sub.2 so that the arithmetic mean thereof is equal to the atmospheric temperature T.sub.0 of the space in which the cooling device is disposed. In conventional cooling water supply systems, no attempts were made to conduct accurate control of the temperature of the cooling water, and the amount of cooling water supplied was fixed in accordance with the maximum load period.
However, in such structures in accordance with this technological background, the water flow resistance of the entire cooling water supply system exceeds, for example, 4 kg/cm.sup.2, and in particular, the cooling pipe RK comprising the central part of the cooling structure comprises a continuous thin metal pipe, so that the water flow resistance within the cooling pipe RK exceeds 1 kg/cm.sup.2, so that problems occur, such as difficulties in suppressing the generation of slight vibration, increases in operating costs of devices including cooling devices accompanying an increase in water flow resistance, and in water supply force, and the fact that a temperature gradient develops over the large range between the flow-in portion LN and the flow-out portion LO of the cooling pipe RK; that is to say, a thermal load distribution is produced in the portion to be cooled, and this causes temperature fluctuations toward the periphery thereof.
For example, about the time of the initiation of cooling water supply to the heat generating section of an EB exposure apparatus, when measurements were made with respect to vibration generation (measurements of the Gal value over time) in the case in which a conventional cooling device was used, it was determined that large detrimental vibration was generated in all directions (2 directions mutually perpendicular within the surface on which the device was disposed, and the direction perpendicular to this surface), particularly after the initiation of cooling water supply.
Among conventional cooling water supply systems, the pressure loss is particularly large in cases in which the water flow resistance of the cooling device is at high pressure (approximately 1 kg/cm.sup.2), so that a correspondingly large amount of energy is transformed into another type of energy, that is to say, vibrational energy or thermal energy, so that this represents a source of vibration generation.
Furthermore, the heat generating section, which is the section to be cooled in conventional cooling devices, has a temperature distribution which varies with the heat generating state, so that this represents a cause of variances in the atmospheric temperature at the periphery of the device.
The present invention solves the problems present in the technological background which were listed above; it is an object thereof to provide a liquid cooled cooling device which is capable of realizing suppression of vibration generation, a reduction of water supply force, and furthermore, the prevention of variation in temperature at the periphery of the heat generating section.